The Contractor shall continue to develop rapid approaches to the sequence analysis of lacI mutants and apply this technology to the sequencing of selected mutant clones derived from the validation experiments being carried out by Stratagene (the developer of the Big Blue(TM) transgenic mouse). The project will (1) confirm the mutagenic response to known carcinogens and compare these responses (and hence mechanism) with known responses in other systems including bacterial and yeast, (2) confirm the tissue specificity number of selected agents by examining the mutational spectra in tissue affected and unaffected by specific agents, (3) examine in more detail the responses of non-genotoxic carcinogens, and (4) confirm the lack of mutational response following treatment with non-genotoxic, non-carcinogenic agents (negative controls). In addition, the work shall provide a detailed spectrum for spontaneous mutation in the various tissues. These spectra will be essential for the assessment of any future applications of the lacI based transgenic mice.